The invention relates to a security braking device.
In a general way, this device is intended to be mounted between a hydraulic fluid tank and actuation members capable of acting on braking members.
The invention can be used to particular advantage when fitted to the brake systems of aircraft weighing less than 5.7 tonnes, in accordance with the international standards currently in force.
It will be recalled that, in a known way, in this type of aircraft, the brakes are mounted onto the main undercarriage wheels and are actuated hydraulically by means of a right pedal and a left pedal. Each of the pedals acts on a master cylinder connected to the braking members of each of the wheels. The brakes are actuated separately by the right and left pedals, thereby also making it possible, as a function of the force applied to one of the pedals, to urge a single master cylinder to pressure for example, in order to lock or slow down one of the wheels thereby, concomitantly, allowing the aircraft to rotate as it moves forward, with a more or less substantial turning radius depending on the pressure applied.
However, with this braking system, it is very difficult to ensure straight-line braking. Indeed, straight-line braking requires identical force on both wheels, this being conveyed by an identical pressure force on each of the two pedals. In reality, it is very difficult, if not almost impossible, to apply an identical pressure force to each of the pedals. When an aircraft is moving around the runway, at very low speed, the consequences of this pressure fluctuation on each of the pedals may be acceptable. This is not however the case when the aircraft reaches high speed, on landing or on takeoff. If, for whatever reason (lack of engine power, too high a speed, etc.), the pilot is forced to apply so-called emergency braking, there is a very high risk of locking one wheel relative to the other thereby immediately causing swiveling and loss of control of the aircraft trajectory, with significant risk of overturning.
Studies have shown that a quarter of the accidents involving this type of aircraft weighing less than 5.7 tonnes occur on landing or on takeoff, subsequent to emergency braking being applied.
The stated purpose of the invention is to overcome these drawbacks in a straightforward, safe, effective and rational way.